Bonding apparatus, bonding system, bonding method, and recording medium

ABSTRACT

A bonding apparatus configured to bond substrates comprises a first holder configured to vacuum-exhaust a first substrate to attract and hold the first substrate on a bottom surface thereof; a second holder disposed under the first holder, and configured to vacuum-exhaust a second substrate to attract and hold the second substrate on a top surface thereof; a mover configured to move the first holder and the second holder relatively in a horizontal direction; a laser interferometer system configured to measure a position of the first holder or the second holder which is moved by the mover; a linear scale configured to measure a position of the mover; and a controller configured to control the mover based on a measurement result of the laser interferometer system and a measurement result of the liner scale.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Patent Application No. 2016-218580 filed on Nov. 9, 2016, the entire disclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The various embodiments described herein pertain generally to a bonding apparatus configured to bond substrates, a bonding system equipped with the bonding apparatus, a bonding method using the bonding apparatus and a recording medium.

BACKGROUND ART

Recently, semiconductor devices are getting miniaturized. If a plurality of highly integrated semiconductor devices is placed on a horizontal plane and these semiconductor devices are connected by a wiring to be produced as a product, a wiring length is increased. As a result, resistance of the wiring is increased, and there is a concern that a wiring delay may be increased.

In this regard, there is proposed using a three-dimensional integration technique of stacking semiconductor devices three-dimensionally. In this three-dimensional integration technique, two sheets of semiconductor wafers (hereinafter, referred to as “wafers”) are bonded by using a bonding system described in, for example, Patent Document 1. By way of example, the bonding system is equipped with a surface modifying apparatus configured to modify to-be-bonded surfaces of wafers; a surface hydrophilizing apparatus configured to hydrophilize the surfaces of the wafers which are modified by the surface modifying apparatus; a bonding apparatus configured to bond the wafers having the surfaces which are hydrophilized by the surface hydrophilizing apparatus. In this bonding system, the surfaces of the wafers are modified in the surface modifying apparatus by performing a plasma processing on the surfaces of the wafers. Further, in the surface hydrophilizing apparatus, the surfaces of the wafers are hydrophilized by supplying pure water onto the surfaces thereof. Then, the wafers are bonded in the bonding apparatus by a Van der Waals force and a hydrogen bond (intermolecular force).

In the aforementioned bonding apparatus, one wafer (hereinafter, referred to as “upper wafer”) is held by using an upper chuck, and the other wafer (hereinafter, referred to as “lower wafer”) is held by a lower chuck provided under the upper chuck. While being held by these upper and lower chucks, the upper wafer and the lower wafer are bonded. Here, before the wafers are bonded, positions of the upper wafer and the lower wafer in a horizontal direction are adjusted by moving the lower chuck in the horizontal direction, and, also, positions of the upper wafer and the lower wafer in a vertical direction are adjusted by moving the lower chuck in the vertical direction.

A mover configured to move the lower chuck in the horizontal direction is moved on a rail which is extended in the horizontal direction (X direction and Y direction). Further, a mover configured to move the lower chuck in the vertical direction includes: a base having a wedge shape (triangular prism shape) with an inclined surface; and a linear guide configured to be movable along a top surface of the base. The linear guide is moved along the base in the horizontal direction and the vertical direction, and, accordingly, the lower chuck supported at the linear guide is moved in the vertical direction.

PRIOR ART DOCUMENT

Patent Document 1: Japanese Patent Laid-open Publication No. 2016-105458

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In the bonding apparatus disclosed in the aforementioned Patent Document 1, when moving the lower chuck in the horizontal direction, a position of the mover in the horizontal direction is measured by using, for example, a linear scale. By feedback-controlling the mover based on the measurement result, the position of the lower chuck in the horizontal direction is adjusted.

Even if, however, the horizontal positions of the upper wafer and the lower wafer are adjusted through the feedback control using the linear scale, the lower chuck may be moved in the horizontal direction as well when it is moved in the vertical direction later as the base of the mover has the wedge shape as stated above. Resultantly, the position of the lower chuck in the horizontal direction may be deviated. Further, since this deviation in the horizontal direction is a deviation of the lower chuck at a load side, this deviation may not be detected with the linear scale which is configured to measure the position of the mover in the horizontal direction. Accordingly, when bonding the wafers, there is a concern that the upper wafer and the lower wafer may be bonded while being deviated from each other. In this regard, there is still a room for improvement in bonding the wafers.

The purpose of exemplary embodiments described herein is to provide a technique capable of performing a bonding processing of bonding substrates appropriately by performing position adjustment of a first holder configured to hold a first substrate and a second holder configured to hold a second substrate appropriately.

Means for Solving the Problems

In one exemplary embodiment, a bonding apparatus configured to bond substrates includes a first holder configured to vacuum-exhaust a first substrate to attract and hold the first substrate on a bottom surface thereof; a second holder disposed under the first holder, and configured to vacuum-exhaust a second substrate to attract and hold the second substrate on a top surface thereof; a mover configured to move the first holder and the second holder relatively in a horizontal direction; a laser interferometer system configured to measure a position of the first holder or the second holder which is moved by the mover; a linear scale configured to measure a position of the mover; and a controller configured to control the mover based on a measurement result of the laser interferometer system and a measurement result of the liner scale.

According to the exemplary embodiment, a position of the first holder or the second holder at a load side can be measured by using the laser interferometer system. Further, a position of the mover can be measured by using the linear scale. Accordingly, even if the first holder or the second holder is deviated in the horizontal direction when moving the first holder or the second holder in a vertical direction as in the prior art, a deviation amount in the horizontal direction can be measured by using the laser interferometer system. Therefore, a relative position between the first holder and the second holder can be appropriately adjusted, and, accordingly, the bonding between the first substrate held by the first holder and the second substrate held by the second holder can be appropriately carried out later.

In another exemplary embodiment, a bonding system equipped with a bonding apparatus includes a processing station equipped with the bonding apparatus; and a carry-in/out station configured to place thereon multiple first substrates, multiple second substrates or multiple combined substrates each obtained by bonding the first substrate and the second substrate, and configured to carry the first substrates, the second substrates or the combined substrates into/from the processing station. The processing station comprises a surface modifying apparatus configured to modify surfaces of the first substrate or the second substrate to be bonded; a surface hydrophilizing apparatus configured to hydrophilize the surfaces of the first substrate or the second substrate modified by the surface modifying apparatus; and a transfer device configured to transfer the first substrates, the second substrates or the combined substrates with respect to the surface modifying apparatus, the surface hydrophilizing apparatus and the bonding apparatus. In the bonding apparatus, the first substrate and the second substrate having the surfaces hydrophilized by the surface hydrophilizing apparatus are bonded.

In yet another exemplary embodiment, in a bonding method of bonding substrates by using a bonding apparatus, the bonding apparatus comprises a first holder configured to vacuum-exhaust a first substrate to attract and hold the first substrate on a bottom surface thereof; a second holder disposed under the first holder, and configured to vacuum-exhaust a second substrate to attract and hold the second substrate on a top surface thereof; a mover configured to move the first holder and the second holder relatively in a horizontal direction; a laser interferometer system configured to measure a position of the first holder or the second holder which is moved by the mover; and a linear scale configured to measure a position of the mover. The bonding method comprises controlling the mover using a measurement result of the laser interferometer system and a measurement result of the linear scale to adjust a relative position between the first holder and the second holder.

In still yet another exemplary embodiment, there is provided a computer-readable recording medium having stored thereon computer-executable instructions that, in response to execution, cause the bonding apparatus to perform the bonding method.

Effect of the Invention

According to the exemplary embodiments as described above, it is possible to perform the bonding processing of bonding the substrates appropriately by performing the position adjustment of the first holder configured to hold the first substrate and the second holder configured to hold the second substrate appropriately.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view schematically illustrating a configuration of a bonding system according to an exemplary embodiment.

FIG. 2 is a side view schematically illustrating an internal configuration of the bonding system according to the exemplary embodiment.

FIG. 3 is a side view schematically illustrating a configuration of an upper wafer and a lower wafer.

FIG. 4 is a transversal cross sectional view schematically illustrating a configuration of a bonding apparatus.

FIG. 5 is a longitudinal cross sectional view schematically illustrating the configuration of the bonding apparatus.

FIG. 6 is a perspective view schematically illustrating an internal configuration of the bonding apparatus.

FIG. 7 is an explanatory diagram illustrating a configuration of a servo loop in a controller.

FIG. 8 is a longitudinal cross sectional view schematically illustrating a configuration of an upper chuck, an upper chuck holder and a lower chuck.

FIG. 9 is a flowchart illustrating major processes of a wafer bonding processing.

FIG. 10 is an explanatory diagram illustrating a state in which a center of the upper wafer and a center of the lower wafer are pressed to be brought into contact with each other.

FIG. 11 is an explanatory diagram illustrating a configuration of a servo loop in a controller according to another exemplary embodiment.

DETAILED DESCRIPTION

Hereinafter, various exemplary embodiments will be described with reference to accompanying drawings. Further, it should be noted that the exemplary embodiments are not intended to be anyway limiting.

1. Configuration of Bonding System

First, a configuration of a bonding system according to an exemplary embodiment will be discussed. FIG. 1 is a plan view schematically illustrating a configuration of a bonding system 1. FIG. 2 is a side view schematically illustrating an internal configuration of the bonding system 1.

In the bonding system 1, two sheets of wafers W_(U) and W_(L) as substrates are bonded, for example, as shown in FIG. 3. Hereinafter, a wafer placed at an upper side is referred to as “upper wafer W_(U)” as a first substrate, and a wafer placed at a lower side is referred to as “lower wafer W_(L)” as a second substrate. Further, in surfaces of the upper wafer W_(U), a bonding surface to be bonded is referred to as “front surface W_(U1),” and a surface opposite to the front surface W_(U1) is referred to as “rear surface W_(U2).” Likewise, in surfaces of the lower wafer W_(L), a bonding surface to be bonded is referred to as “front surface W_(L1),” and a surface opposite to the front surface W_(L1) is referred to as “rear surface W_(L2).” In the bonding system 1, a combined wafer W_(T) as a combined substrate is formed by bonding the upper wafer W_(U) and the lower wafer W_(L).

The bonding system 1 is equipped with, as depicted in FIG. 1, a carry-in/out station 2 and a processing station 3 connected as a single body. The carry-in/out station 2 is configured to carry cassettes C_(U), C_(L) and C_(T), which accommodates therein a plurality of wafers W_(U), a plurality of wafers W_(L) and a plurality of combined wafers W_(T), respectively, to/from the outside. The processing station 3 is equipped with various kinds of processing apparatuses configured to perform preset processings on the wafers W_(U) and W_(L) and the combined wafer W_(T).

The carry-in/out station 2 includes a cassette placing table 10. The cassette placing table 10 is equipped with a multiple number of, for example, four cassette placing plates 11. The cassette placing plates 11 are arranged in a horizontal X direction (up-and-down direction of FIG. 1). When the cassettes C_(U), C_(L), C_(T) are carried to/from the outside of the bonding system 1, the cassettes C_(U), C_(L), C_(T) are placed on these cassette placing plates 11. In this way, the carry-in/out station 2 is configured to be capable of holding a multiple number of upper wafers W_(U), a multiple number of lower wafers W_(L) and a multiple number of combined wafers W_(T). Further, the number of the cassette placing tables 11 is not limited to the example shown in the present exemplary embodiment, and may be set as required. Furthermore, one of the cassettes may be used to collect abnormal wafers. That is, an abnormal combined wafer, which has suffered a problem in bonding between an upper wafer W_(U) and a lower wafer W_(L), is separately accommodated in a cassette to be separated from other normal combined wafers W_(T). In the present exemplary embodiment, one of the cassettes C_(T) is used for the collection of the abnormal wafers, and other cassettes C_(T) are used for the accommodation of the normal combined wafers W_(T).

The carry-in/out station 2 is equipped with a wafer transfer section 20 adjacent to the cassette placing table 10. Provided in the wafer transfer section 20 is a wafer transfer device 22 configured to be movable along a transfer path 21 which is extended in the X direction. The wafer transfer device 22 is configured to be movable in a vertical direction and pivotable around a vertical axis (θ direction). The transfer device 22 is configured to transfer the wafers W_(U) and W_(L) and the combined wafer W_(T) between the cassettes C_(U), C_(L)and C_(T) placed on the cassette placing plates 11 and transition devices 50 and 51 of a third processing block G3 of the processing station 3 to be described later.

A multiple number of, for example, three processing blocks G1, G2 and G3 equipped with various kinds of apparatuses are provided in the processing station 3. For example, the first processing block G1 is provided at a front side (negative X-directional side of FIG. 1) of the processing station 3, and the second processing block G2 is provided at a rear side (positive X-directional side of FIG. 1) of the processing station 3. Further, the third processing block G3 is provided near the carry-in/out station 2 (at a negative Y direction side of FIG. 1) of the processing station 3.

Provided in the first processing block G1 is a surface modifying apparatus 30 configured to modify the surfaces W_(U1) and W_(L1) of the wafers W_(U) and W_(L). In the surface modifying apparatus 30, an oxygen gas or a nitrogen gas as a processing gas is formed into plasma under a decompressed atmosphere to be ionized. These oxygen ions or nitrogen ions are irradiated to the surfaces W_(U1) and W_(L1) of the wafers W_(U) and W_(L), so the surfaces W-_(U1) and W_(L1) are plasma-processed to be modified.

By way of example, in the second processing block G2, a surface hydrophilizing apparatus 40 and a bonding apparatus 41 are arranged in a horizontal Y direction in this sequence from the carry-in/out station 2. The surface hydrophilizing apparatus 40 is configured to hydrophilize and clean the surfaces W_(U1) and W_(L1) of the wafers W_(U) and W_(L) with, for example, pure water. The bonding apparatus 41 is configured to bond the wafers W_(U) and W_(L). A configuration of the bonding apparatus 41 will be elaborated later.

In this surface hydrophilizing apparatus 40, while rotating the wafer W_(U) (W_(L)) held by, for example, a spin chuck, the pure water is supplied onto the corresponding wafer W_(U) (W_(L)). The supplied pure water is diffused on the surface W_(U1) (W_(L1)) of the wafer W_(U) (W_(L)), so that the surface W_(U1) (W_(L1)) is hydrophilized.

By way of example, in the third processing block G3, the transition devices 50 and 51 for the wafers W_(U) and W_(L) and the combined wafer W_(T) are arranged in two levels in this order from the bottom, as illustrated in FIG. 2.

Further, as illustrated in FIG. 1, a wafer transfer region 60 is formed in an area surrounded by the first processing block G1 to the third processing block G3. For example, a wafer transfer device 61 is disposed in the wafer transfer region 60.

The wafer transfer device 61 is equipped with, for example, a transfer arm 61 a which is configured to be movable in a vertical direction and a horizontal direction (Y direction and X direction) and pivotable around a vertical axis. The wafer transfer device 61 is moved within the wafer transfer region 60 and transfers the wafers W_(U) and W_(L) and the combined wafer W_(T) into preset apparatuses within the first processing block G1, the second processing block G2 and the third processing block G3 which are adjacent to the wafer transfer region 60.

As depicted in FIG. 1, the bonding system 1 is equipped with a controller 70. The controller 70 may be implemented by, for example, a computer and includes a program storage (not shown). The program storage stores therein programs for controlling processings on the wafers W_(U) and W_(L) and the combined wafer W_(T) in the bonding system 1. Further, the program storage also stores therein programs for controlling operations of the aforementioned various kinds of the processing apparatuses and a driving system such as the transfer devices to thereby allow a wafer bonding processing to be described later to be performed in the bonding system 1. Further, the programs are stored in, for example, a computer-readable recording medium H such as a hard disk (HD), a flexible disk (FD), a compact disk (CD), a magnet optical disk (MO) or a memory card, and may be installed to the controller 70 from the recording medium H.

2. Configuration of Bonding Apparatus

Now, a configuration of the bonding apparatus 41 will be explained.

2-1. Overall Configuration of Bonding Apparatus

As depicted in FIG. 4 and FIG. 5, the bonding apparatus 41 includes a processing chamber 100 having a hermetically sealable inside. A carry-in/out opening 101 for the wafers W_(U) and W_(L) and the combined wafer W_(T) is formed at a lateral side of the processing vessel 100 on the side of the wafer transfer region 60. An opening/closing shutter 102 for the carry-in/out opening 101 is provided at the carry-in/out opening 101.

The inside of the processing vessel 100 is partitioned into a transfer region T1 and a processing region T2 by an inner wall 103. The aforementioned carry-in/out opening 101 is formed at the lateral side of the processing vessel 100 in the transfer region T1. Further, the inner wall 103 is also provided with a carry-in/out opening 104 for the wafers W_(U) and W_(L) and the combined wafer W_(T).

A transition 110 configured to temporarily place thereon the wafers W_(U) and W_(L) and the combined wafer W_(T) is provided at a positive Y-directional side of the transfer region T1. The transition 110 has, for example, two levels and is capable of holding any two of the wafers W_(U) and W_(L) and the combined wafer W_(T) at the same time.

A wafer transfer device 111 is provided within the transfer region T1. The wafer transfer device 111 is equipped with a transfer arm 111 a configured to be movable in the vertical direction and the horizontal direction (X direction and Y direction) and also pivotable around a vertical axis. The wafer transfer device 111 is capable of transferring the wafers W_(U) and W_(L) and the combined wafer W_(T) within the transfer region T1 or between the transfer region T1 and the processing region T2.

A position adjusting device 120 configured to adjust a direction of the wafers W_(U) and W_(L) in the horizontal direction is provided at a negative Y-directional side of the transfer region T1. The position adjusting device 120 includes: a base 121 equipped with a holder (not shown) configured to hold and rotate the wafer W_(U) (W_(L)); and a detector 122 configured to detect a position of a notch of the wafer W_(U) (W_(L)). The position adjusting device 120 adjusts the position of the notch of the wafer W_(U) (W_(L)) by detecting the position of the notch with the detector 122 while rotating the wafer W_(U) (W_(L)) held by the base 121. Accordingly, the horizontal positions of the wafer W_(U) (W_(L)) is adjusted. Further, a structure configured to hold the wafer W_(U) (W_(L)) in the base 121 is not particularly limited. By way of non-limiting example, various structures such as a pin chuck structure or a spin chuck structure may be utilized.

Furthermore, an inverting device 130 configured to invert a front surface and a rear surface of the upper wafer W_(U) is provided in the transfer region T1. The inverting device 130 is equipped with a holding arm 131 configured to hold the upper wafer W_(U). The holding arm 131 is extended in the horizontal direction (X direction). Further, the holding arm 131 is provided with holding members 132 respectively arranged at four positions. The holding members 132 are configured to hold the upper wafer W_(U).

The holding arm 131 is supported by a driver 133 including, for example, a motor or the like. The holding arm 131 is configured to be rotatable around a horizontal axis by the driver 133. Further, the holding arm 131 is rotatable around the driver 133 and movable in the horizontal direction (X direction). Another driver (not shown) including, for example, a motor or the like is provided under the driver 133. The driver 133 can be moved in the vertical direction along a vertically extended supporting column 134 by this another driver. The upper wafer W_(U) held by the holding members 132 can be rotated around the horizontal axis and can also be moved in the vertical direction and the horizontal direction by the driver 133. Further, the upper wafer W_(U) held by the holding members 132 can be moved between the position adjusting device 120 and an upper chuck 140 to be described later by being rotated around the driver 133.

The upper chuck 140 and a lower chuck 141 are disposed in the processing region T2. The upper chuck 140 serves as a first holder configured to attract and hold the upper wafer W_(U) on a bottom surface thereof, and the lower chuck 141 serves as a second holder configured to place the lower wafer W_(L) on a top surface thereof while attracting and holding the lower wafer W_(L). The lower chuck 141 is provided under the upper chuck 140 and is configured to be disposed to face the upper chuck 140. That is, the upper wafer W_(U) held by the upper chuck 140 and the lower wafer W_(L) held by the lower chuck 141 can be arranged to face each other.

The upper chuck 140 is held by an upper chuck holder 150 disposed above the upper chuck 140. The upper chuck holder 150 is provided at a ceiling surface of the processing vessel 100. That is, the upper chuck 140 is fixed to the processing vessel 100 with the upper chuck holder 150 therebetween.

The upper chuck holder 150 is equipped with an upper imaging device 151 configured to image the front surface W_(L1) of the lower wafer W_(L) held by the lower chuck 141. That is, the upper imaging device 151 is disposed adjacent to the upper chuck 140. The upper imaging device 151 may be, by way of example, but not limitation, a CCD camera.

As depicted in FIG. 4 to FIG. 6, the lower chuck 141 is supported by a lower chuck stage 160 provided under the lower chuck 141. The lower chuck stage 160 is equipped with a lower imaging device 161 configured to image the front surface W_(U1) of the upper wafer W_(U) held by the upper chuck 140. That is, the lower imaging device 161 is disposed adjacent to the lower chuck 141. The lower imaging device 161 may be, by way of example, but not limitation, a CCD camera.

The lower chuck stage 160 is supported by a first lower chuck mover 162 disposed under the lower chuck stage 160. Further, the first lower chuck mover 162 is supported by a supporting table 163. The first lower chuck mover 162 is configured to move the lower chuck 141 in the horizontal direction (X direction) as will be described later.

Further, the first lower chuck mover 162 is configured to be capable of moving the lower chuck 141 in the vertical direction. To elaborate, the first lower chuck mover 162 may have the same structure as a first lower chuck mover described in Japanese Patent Laid-open Publication No. 2016-105458. That is, the first lower chuck mover 162 is equipped with: a base having a wedge shape (triangular prism shape) with an inclined top surface; a rail disposed on the top surface of the base; and a linear guide configured to be movable along the rail. As the linear guide is moved along the rail, the lower chuck supported by the linear guide is moved in the vertical direction.

Further, the first lower chuck mover 162 is configured to be rotatable around a vertical axis.

The supporting table 163 is fastened to a pair of rails 164 which is disposed at a bottom side of the supporting table 163 to be elongated in the horizontal direction (X direction). The supporting table 163 is configured to be movable along the rails 164 by the first lower chuck mover 162. Further, the first lower chuck mover 162 is moved by, for example, a linear motor (not shown) provided along the rails 164.

The rails 164 are provided at a second lower chuck mover 165. The second lower chuck mover 165 is fastened to a pair of rails 166 which is provided at a bottom side of the second lower chuck mover 165 to be elongated in the horizontal direction (Y direction). The second lower chuck mover 165 is configured to be movable along the rails 166, that is, to move the lower chuck 141 in the horizontal direction (Y direction). The second lower chuck mover 165 is moved by, for example, a linear motor (not shown) provided along the rails 166. The rails 166 are disposed on a placing table 167 provided at a bottom surface of the processing vessel 100.

2-2. Servo Control Over Lower Chuck Movers

Now, a movement of the first lower chuck mover 162 and a servo control of the second lower chuck mover 165 in the bonding apparatus 41 will be explained. The servo control in the present exemplary embodiment is a hybrid control using a laser interferometer and a linear scale.

The bonding apparatus 41 is equipped with a laser interferometer system 170 configured to measure a position of the lower chuck 141 in the horizontal direction. The laser interferometer system 170 includes a laser head 171, optical path changers 172 and 173, reflection plates 174 and 175 and laser interferometers 176 and 177. Further, a commonly known method is used to measure the position of the lower chuck 141 in the laser interferometer system 170.

The laser head 171 is a light source configured to emit a laser beam. The laser head 171 is substantially on the level with a top surface of a placing table 167 and is provided at an end side of the placing table 167 in the negative Y direction and provided at a center of the placing table 167 in the X direction. The laser head 171 is supported by a supporter (not shown) provided at an outside of the placing table 167.

The optical path changers 172 and 173 are respectively configured to change an optical path of the laser beam emitted from the laser head 171. The first optical path changer 172 is configured to change the optical path of the laser beam from the laser head 171 to a vertically upward direction. The first optical path changer 172 is substantially on the level with the top surface of the placing table 167, and is disposed at an end side of the placing table 167 in the positive X direction and disposed at an end side of the placing table 167 in the negative Y direction. Further, the first optical path changer 172 is supported by a supporter (not shown) provided at the outside of the placing table 167.

The second optical path changer 173 is configured to branch the laser beam from the first optical path changer 172 toward the first laser interferometer 176 (negative X direction) and the second laser interferometer 177 (positive Y direction) respectively. The second optical path changer 173 is substantially on the level with a top surface of the lower chuck stage 160 and is disposed at an end side of the placing table 167 in the positive X direction and disposed at an end side of the placing table 167 in the negative Y direction. Further, the second optical path changer 173 is supported by a supporter (not shown) provided at the outside of the placing table 167.

The first reflection plate 174 is configured to reflect the laser beam from the first laser interferometer 176. The first reflection plate 174 is disposed to face the first laser interferometer 176 on the top surface of the lower chuck stage 160 at the negative Y direction side. The first reflection plate 174 is extended in the X direction. A length of the first reflection plate 174 in the X direction is set to be equal to or larger than a moving distance (stroke length) of the lower chuck stage 160 in the X direction such that the first reflection plate 174 is capable of reflecting the laser beam from the first laser interferometer 176 all the time even if the lower chuck stage 160 is moved in the X direction. Likewise, a length of the first reflection plate 174 in the vertical direction is set to be equal to or larger than a moving distance (stroke length) of the lower chuck stage 160 in the vertical direction.

The second reflection plate 175 is configured to reflect the laser beam from the second laser interferometer 177. The second reflection plate 175 is disposed to face the second laser interferometer 177 on the top surface of the lower chuck stage 160 at the positive X direction side. The second reflection plate 175 is extended in the Y direction. A length of the second reflection plate 175 in the Y direction is set to be equal to or larger than a moving distance (stroke length) of the lower chuck stage 160 in the Y direction such that the second reflection plate 175 is capable of reflecting the laser beam from the second laser interferometer 177 all the time even if the lower chuck stage 160 is moved in the Y direction. Likewise, a length of the second reflection plate 175 in the vertical direction is set to be equal to or larger than a moving distance (stroke length) of the lower chuck stage 160 in the vertical direction.

The first laser interferometer 176 is configured to measure a position of the lower chuck 141 in the X direction by using the laser beam from the second optical path changer 173 and the reflection light from the first reflection plate 174. The first laser interferometer 176 is substantially on the level with the top surface of the lower chuck stage 160, and is disposed at the central position of the placing table 167 in the X direction and disposed at the end side of the placing table 167 in the negative Y direction. Further, the first laser interferometer 176 is supported by a supporter (not shown) provided at the outside of the placing table 167. Further, the first laser interferometer 176 is connected with a detector (not shown).

The second laser interferometer 177 is configured to measure a position of the lower chuck 141 in the Y direction by using the laser beam from the second optical path changer 173 and the reflection light from the second reflection plate 175. The second laser interferometer 177 is substantially on the level with the top surface of the lower chuck stage 160, and is disposed at the end side of the placing table 167 in the positive X direction and disposed at the center position of the placing table 167 in the Y direction. Further, the second laser interferometer 177 is supported by a supporter (not shown) provided at the outside of the placing table 167. Furthermore, the second laser interferometer 177 is connected with a detector (not shown).

Further, the bonding apparatus 41 is equipped with a first linear scale 181 configured to measure a position of the first lower chuck mover 162 in the X direction and a second linear scale 182 configured to measure a position of the second lower chuck mover 165 in the Y direction. The first linear scale 181 is provided on the second lower chuck mover 165 along the rail 164. The second linear scale 182 is provided on the placing table 167 along the rail 166. For the measurement of the positions of the lower chuck movers 162 and 165 by these linear scales 181 and 182, a commonly known method may be used.

Measurement results of the laser interferometer system 170 and measurement results of the linear scales 181 and 182 are outputted to the aforementioned controller 70, and the controller 70 performs a servo control over the lower chuck movers 162 and 165 based on these measurement results. FIG. 7 is an explanatory diagram illustrating a configuration of a servo loop in the controller 70.

The controller 70 has a position loop and a speed loop as the servo loop. The measurement results of the laser interferometers 176 and 177 are used in the position loop, and the positions of the lower chuck movers 162 and 165 are feedback-controlled. The measurement results of the linear scales 181 and 182 are used in the speed loop, and the speeds of the lower chuck movers 162 and 165 are feedback-controlled. Further, the measurement results of the laser interferometers 176 and 177 are also used as speed instructions.

Here, the second linear scale 182 is placed in the vicinity of the second lower chuck mover 165, and the measurement result of the second linear scale 182 is fed back to the second lower chuck mover 165 as highly stable data. Therefore, responsiveness can be improved by increasing a gain of the speed loop, so that a rapid control can be carried out.

Meanwhile, a distance between the second laser interferometer 177 configured to measure the position of the lower chuck 141 at the load side and the second lower chuck mover 165 (linear motor) in the vertical direction is about 300 mm. That is, the second laser interferometer 177 and the second lower chuck mover 165 are spaced apart from each other, and a structure provided between the lower chuck 141 and the second lower chuck mover 165 is not a rigid body. Accordingly, the measurement result of the second laser interferometer 177 is fed back to the second lower chuck mover 165 as low-stability data. In such a case, if the measurement result of the second laser interferometer 177 is put in the speed loop and the rapid control with the improved responsiveness by increasing the gain as stated above is performed, the movement of the second lower chuck mover 165 may be oscillated, so that it may be impossible to control the second lower chuck mover 165. Furthermore, if the measurement result of the second laser interferometer 177 is put in the speed loop, it may be considered to perform a slow control with lowered responsiveness by decreasing the gain. In such a case, however, the position of the second lower chuck mover 165 may not be stabilized.

Therefore, to perform a control with the high responsiveness, it is desirable to use the measurement result of the second linear scale 182 in the speed loop.

Meanwhile, in the second linear scale 182, the position of the lower chuck 141 at the load side cannot be measured. Accordingly, even if the position of the lower chuck 141 is deviated, for example, such a deviation may not be detected. Thus, it is desirable to use the measurement result of the second laser interferometer 177 in the position loop.

As stated above, if the measurement result of the second laser interferometer 177 is used in the position loop and the measurement result of the second linear scale 182 is used in the speed loop, it is possible to return the second lower chuck mover 165 to an appropriate position when there is a change in the lower chuck 141 while being capable of detecting the position of the lower chuck 141 at the load side.

For the same reason, the measurement result of the first laser interferometer 176 is used in the position loop, and the measurement result of the first linear scale 181 is used in the speed loop.

As described above, in the servo control over the lower chuck movers 162 and 165, by performing the hybrid control using the measurement results of the laser interferometer system 170 and the measurement results of the linear scales 181 and 182, the lower chuck movers 162 and 165 can be controlled appropriately.

2-3. Configuration of Upper Chuck and Upper Chuck Holder

Now, a detailed configuration of the upper chuck 140 and the upper chuck holder 150 of the bonding apparatus 41 will be discussed.

The upper chuck 140 is of a pin chuck type, as shown in FIG. 8. The upper chuck 140 has a main body 190 having a diameter larger than a diameter of the upper wafer W_(U) when viewed from the top. A plurality of pins 191 configured to be brought into contact with the rear surface W_(U2) of the upper wafer W_(U) is provided at a bottom surface of the main body 190. Further, an outer rib 192 having the same height as the pins 191 and configured to support a periphery of the rear surface W_(U2) of the upper wafer W_(U) is provided at a periphery of the bottom surface of the main body 190. The outer rib 192 is annularly formed at an outside of the pins 191.

Further, an inner rib 193 having the same height as the pins 191 and configured to support the rear surface W_(U2) of the upper wafer W_(U) is provided at an inside of the outer rib 192 on the bottom surface of the main body 190. The inner rib 193 is formed in a ring shape to be concentric with the outer rib 192. A region 194 inside the outer rib 192 (hereinafter, sometimes referred to as “suction region 194”) is partitioned into a first suction region 194 a inside the inner rib 193 and a second suction region 194 b outside the inner rib 193.

First suction openings 195 a for vacuum-exhausting the upper wafer W_(U) in the first suction region 194 a are formed at the bottom surface of the main body 190. The first suction openings 195 a are formed at, for example, four positions in the first suction region 194 a. The first suction openings 195 a are connected to first suction lines 196 a which are provided within the main body 190. Further, the first suction lines 196 a are connected with a first vacuum pump 197 a.

In addition, second suction openings 195 b for vacuum-exhausting the upper wafer W_(U) in the second suction region 194 b are formed at the bottom surface of the main body 190. The second suction openings 195 b are formed at, for example, two positions within the second suction region 194 b. The second suction openings 195 b are connected to second suction lines 196 b provided within the main body 190. Further, the second suction lines 196 b are connected with a second vacuum pump 197 b.

By vacuum-exhausting the suction regions 194 a and 194 b formed by being surrounded by the upper wafer W_(U), the main body 190 and the outer rib 192 through the suction openings 195 a and 195 b, respectively, the suction regions 194 a and 194 b are decompressed. At this time, since an atmosphere at the outside of the suction regions 194 a and 194 b is under an atmospheric pressure, the upper wafer W_(U) is pressed toward the suction regions 194 a and 194 b by the atmospheric pressure as much as a decompressed amount, so that the upper wafer W_(U) is attracted to and held by the upper chuck 140. Further, the upper chuck 140 is configured to be capable of vacuum-exhausting the upper wafer W_(U) through the first suction region 194 a and the second suction region 194 b individually.

In this case, since the outer rib 192 supports the periphery of the rear surface W_(U2) of the upper wafer W_(U), the upper wafer W_(U) is appropriately vacuum-exhausted, including the periphery thereof. Therefore, the entire surface of the upper wafer W_(U) is attracted to and held by the upper chuck 140, and flatness of the upper wafer W_(U) can be reduced and the upper wafer W_(U) can thus be flattened.

Furthermore, since the heights of the pins 191 are uniform, flatness of the bottom surface of the upper chuck 140 can be further reduced. In this way, by flattening the bottom surface (by reducing the flatness of the bottom surface) of the upper chuck 140, the upper wafer W_(U) held by the upper chuck 140 can be suppressed from suffering from a deformation in the vertical direction.

Further, since the rear surface W_(U2) of the upper wafer W_(U) is supported by the pins 191, it is easy for the upper wafer W_(U) to be separated from the upper chuck 140 when releasing the vacuum-exhaust of the upper wafer W_(U) by the upper chuck 140.

The upper chuck 140 is provided with a through hole 198 which is formed through a center of the main body 190 in a thickness direction of the main body 190. The center of this main body 190 corresponds to a center of the upper wafer W_(U) held by and attracted to the upper chuck 140. A leading end of an actuator 211 of a pressing member 210 to be described later is inserted through this through hole 198.

The upper chuck holder 150 is equipped with an upper chuck stage 200 provided on a top surface of the main body 190 of the upper chuck 140, as depicted in FIG. 5. When viewed from the top, the upper chuck stage 200 is configured to cover at least the top surface of the main body 190 and is fastened to the main body 190 by, for example, a screw. The upper chuck stage 200 is supported by a plurality of supporting members 201 provided at the ceiling surface of the processing vessel 100.

The pressing member 210 configured to press the center of the upper wafer W_(U) is further provided on a top surface of the upper chuck stage 200, as shown in FIG. 8. The pressing member 210 has the actuator 211 and a cylinder 212.

The actuator 211 is configured to generate a constant pressure in a certain direction by air supplied from an electro-pneumatic regulator (not shown), and is capable of generating the pressure constantly regardless of a position of a point of application of the pressure. The actuator 211 is capable of controlling a pressing load applied to the center of the upper wafer W_(U) by the air from the electro-pneumatic regulator while the actuator 211 comes into contact with the center of the upper wafer W_(U). Further, the leading end of the actuator 211 is vertically movable up and down through the through hole 198 by the air from the electro-pneumatic regulator.

The actuator 211 is supported by the cylinder 212. The cylinder 212 is capable of moving the actuator 211 in the vertical direction by a driver having, for example, a motor embedded therein.

As stated above, the pressing member 210 controls the pressing load with the actuator 211 and controls the movement of the actuator 211 with the cylinder 212. The pressing member 210 is capable of pressing the center of the upper wafer W_(U) and a center of the lower wafer W_(L) when bonding of the wafers W_(U) and W_(L) to be described later is performed.

2-4. Configuration of Lower Chuck

Now, a detailed configuration of the lower chuck 141 of the bonding apparatus 41 will be explained.

The lower chuck 141 is of a pin chuck type, the same as the upper chuck 140, as shown in FIG. 8. The lower chuck 141 has a main body 220 having a diameter larger than a diameter of the lower wafer W_(L) when viewed from the top. A plurality of pins 221 configured to be brought into contact with the rear surface W_(L2) of the lower wafer W_(L) is provided at a top surface of the main body 220. Further, an outer rib 222 having the same height as the pins 221 and configured to support a periphery of the rear surface W_(L2) of the lower wafer W_(L) is provided at a periphery of the top surface of the main body 220. The outer rib 222 is annularly formed at an outside of the pins 221.

Further, an inner rib 223 having the same height as the pins 221 and configured to support the rear surface W_(L2) of the lower wafer W_(L) is provided at an inside of the outer rib 222 on the top surface of the main body 220. The inner rib 223 is formed in a ring shape to be concentric with the outer rib 222. A region 224 inside the outer rib 222 (hereinafter, sometimes referred to as “suction region 224”) is partitioned into a first suction region 224 a inside the inner rib 223 and a second suction region 224 b outside the inner rib 223.

A first suction opening 225 a for vacuum-exhausting the lower wafer W_(L) in the first suction region 224 a is formed at the top surface of the main body 220. The first suction opening 225 a is formed at, for example, a single position in the first suction region 224 a. The first suction opening 225 a is connected to a first suction line 226 a which is provided within the main body 220. Further, the first suction line 226 a is connected with a first vacuum pump 227 a.

In addition, second suction openings 225 b for vacuum-exhausting the lower wafer W_(L) in the second suction region 224 b are formed at the top surface of the main body 220. The second suction openings 225 b are formed at, for example, two positions within the second suction region 224 b. The second suction openings 225 b are connected to second suction lines 226 b provided within the main body 220. Further, the second suction lines 226 b are connected with a second vacuum pump 227 b.

By vacuum-exhausting the suction regions 224 a and 224 b formed by being surrounded by the lower wafer W_(L), the main body 220 and the outer rib 222 through the suction openings 225 a and 225 b, respectively, the suction regions 224 a and 224 b are decompressed. At this time, since an atmosphere at the outside of the suction regions 224 a and 224 b is under the atmospheric pressure, the lower wafer W_(L) is pressed toward the suction regions 224 a and 224 b by the atmospheric pressure as much as a decompressed amount, so that the lower wafer W_(L) is attracted to and held by the lower chuck 141. Further, the lower chuck 141 is configured to be capable of vacuum-exhausting the lower wafer W_(L) through the first suction region 224 a and the second suction region 224 b individually.

In this case, since the outer rib 222 supports the periphery of the rear surface W_(L2) of the lower wafer W_(L), the lower wafer W_(L) is appropriately vacuum-exhausted, including the periphery thereof. Therefore, the entire surface of the lower wafer W_(L) is attracted to and held by the lower chuck 141, and flatness of the lower wafer W_(L) can be reduced and the lower wafer W_(L) can thus be flattened.

Furthermore, since the heights of the pins 221 are uniform, flatness of the top surface of the lower chuck 141 can be further reduced. In this way, by flattening the top surface (by reducing the flatness of the top surface) of the lower chuck 141, the lower wafer W_(L) held by the lower chuck 141 can be suppressed from suffering from a deformation in a vertical direction.

Further, since the rear surface W_(L2) of the lower wafer W_(L) is supported by the pins 221, it is easy for the lower wafer W_(L) to be separated from the lower chuck 141 when releasing the vacuum-exhaust of the lower wafer W_(L) by the lower chuck 141.

The lower chuck 141 is provided with through holes (not shown) which are formed in a thickness direction of the main body 220 at, e.g., three positions in the vicinity of a center of the main body 220. Elevating pins provided under the first lower chuck mover 162 are inserted through these through holes.

Guide members (not shown) are provided at a periphery of the main body 220 to suppress each of the wafers W_(U) and W_(L) and the combined wafer W_(T) from falling down by being bounced off or slid off the lower chuck 141. The guide members are equi-spaced at plural positions, for example, four positions at the periphery of the main body 220.

The operations of the individual components of the bonding apparatus 41 are controlled by the aforementioned controller 70.

3. Bonding Method

Now, a bonding method for the wafers W_(U) and W_(L) performed by the bonding system 1 configured as described above will be explained. FIG. 9 is a flowchart illustrating an example of main processes of such a wafer bonding processing.

First, a cassette C_(U) accommodating the upper wafers W_(U), a cassette C_(L) accommodating the lower wafers W_(L) and an empty cassette C_(T) are placed on the preset cassette placing plates 11 of the carry-in/out station 2. Then, an upper wafer W_(U) is taken out of the cassette C_(U) by the wafer transfer device 22 and is transferred to the transition device 50 of the third processing block G3 of the processing station 3.

Subsequently, the upper wafer W_(U) is transferred into the surface modifying apparatus 30 of the first processing block G1 by the wafer transfer device 61. In the surface modifying apparatus 30, an oxygen gas or a nitrogen gas as the processing gas is excited into plasma to be ionized under the preset decompressed atmosphere. The oxygen ions or the nitrogen ions are irradiated to the front surface W_(U1) of the upper wafer W_(U), and the front surface W_(U1) is plasma-processed. As a result, the front surface W_(U1) of the upper wafer W_(U) is modified (process S1 of FIG. 9).

Then, the upper wafer W_(U) is transferred into the surface hydrophilizing apparatus 40 of the second processing block G2 by the wafer transfer device 61. In the surface hydrophilizing apparatus 40, pure water is supplied onto the upper wafer W_(U) while rotating the upper wafer W_(U) held by the spin chuck. The supplied pure water is diffused on the front surface W_(U1) of the upper wafer W_(U), and hydroxyl groups (silanol groups) adhere to the front surface W_(U1) of the upper wafer W_(U) modified in the surface modifying apparatus 30, so that the front surface W_(U1) is hydrophilized. Further, the front surface W_(U1) of the upper wafer W_(U) is cleaned by the pure water (process S2 of FIG. 9).

Thereafter, the upper wafer W_(U) is transferred into the bonding apparatus 41 of the second processing block G2 by the wafer transfer device 61. The upper wafer W_(U) carried into the bonding apparatus 41 is then transferred into the position adjusting device 120 through the transition 110 by the wafer transfer device 111. Then, the direction of the upper wafer W_(U) in the horizontal direction is adjusted by the position adjusting device 120 (process S3 of FIG. 9).

Then, the upper wafer W_(U) is delivered onto the holding arm 131 of the inverting device 130 from the position adjusting device 120. Then, in the transfer region T1, by inverting the holding arm 131, the front surface and the rear surface of the upper wafer W_(U) are inverted (process S4 of FIG. 9). That is, the front surface W_(U1) of the upper wafer W_(U) is turned to face downwards.

Thereafter, the holding arm 131 of the inverting device 130 is rotated around the driver 133 to be located under the upper chuck 140. The upper wafer W_(U) is then transferred to the upper chuck 140 from the inverting device 130. The rear surface W_(U2) of the upper wafer W_(U) is attracted to and held by the upper chuck 140 (process S5 of FIG. 9). To elaborate, by operating the vacuum pumps 197 a and 197 b, the upper wafer W_(U) is vacuum-exhausted through the suction openings 195 a and 195 b in the suction regions 194 a and 194 b, so that the upper wafer W_(U) is attracted to and held by the upper chuck 140.

While the above-described processes S1 to S5 are being performed on the upper wafer W_(U), processings are performed on the lower wafer W_(L). First, the lower wafer W_(L) is taken out of the cassette C_(L) by the wafer transfer device 22 and transferred into the transition device 50 of the processing station 3.

Subsequently, the lower wafer W_(L) is transferred into the surface modifying apparatus 30 by the wafer transfer device 61, and the front surface W_(L1) of the lower wafer W_(L) is modified (process S6 of FIG. 9). Further, the modification of the front surface W_(L1) of the lower wafer W_(L) in the process S6 is the same as the above-described process S1.

Thereafter, the lower wafer W_(L) is transferred into the surface hydrophilizing apparatus 40 by the wafer transfer device 61, so that the front surface W_(L1) of the lower wafer W_(L) is hydrophilized and cleaned (process S7 of FIG. 9). The hydrophilizing and the cleaning of the front surface W_(L1) of the lower wafer W_(L) in the process S7 are the same as those in the above-described process S2.

Afterwards, the lower wafer W_(L) is transferred into the bonding apparatus 41 by the wafer transfer device 61. The lower wafer W_(L) carried into the bonding apparatus 41 is transferred into the position adjusting device 120 through the transition 110 by the wafer transfer device 111. Then, the direction of the lower wafer W_(L) in the horizontal direction is adjusted by the position adjusting device 120 (process S8 of FIG. 9).

Then, the lower wafer W_(L) is transferred onto the lower chuck 141 by the wafer transfer device 111, and the rear surface W_(L2) is attracted to and held by the lower chuck 141 (process S9 of FIG. 9). To elaborate, by operating the vacuum pumps 227 a and 227 b, the lower wafer W_(L) is vacuum-exhausted through the suction openings 225 a and 225 b in the suction regions 224 a and 224 b, so that the lower wafer W_(L) is attracted to and held by the lower chuck 141.

Subsequently, position adjustment between the upper wafer W_(U) held by the upper chuck 140 and the lower wafer W_(L) held by the lower chuck 141 in the horizontal direction is performed. To elaborate, the lower chuck 141 is moved in the horizontal direction (X direction and Y direction) by the first lower chuck mover 162 and the second lower chuck mover 165, and preset reference points on the front surface W_(L1) of the lower wafer W_(L) are imaged in sequence by using the upper imaging device 151. Concurrently, preset reference points on the front surface W_(U1) of the upper wafer W_(U) are imaged in sequence by using the lower imaging device 161. The obtained images are outputted to the controller 70. Based on the images obtained by the upper imaging device 151 and the lower imaging device 161, the controller 70 moves the lower chuck 141 by the first lower chuck mover 162 and the second lower chuck mover 165 to a position where the reference points of the upper wafer W_(U) and the lower wafer W_(L) are overlapped. In this way, the positions of the upper wafer W_(U) and the lower wafer W_(L) in the horizontal direction are adjusted (process S10 of FIG. 9).

In the process S10, the position of the lower chuck 141 in the X direction is measured by using the first laser interferometer 176, and the position of the lower chuck 141 in the Y direction is measured by using the second laser interferometer 177. Further, the position of the first lower chuck mover 162 in the X direction is measured by using the first linear scale 181, and the position of the second lower chuck mover 165 in the Y direction is measured by using the second linear scale 182. When moving the lower chuck movers 162 and 165, the lower chuck movers 162 and 165 are servo-controlled by using the servo loop shown in FIG. 7, that is, by using the position loop using the measurement results of the laser interferometer system 170 and the speed loop using the measurement results of the linear scales 181 and 182. By performing the hybrid control using the laser interferometer system 170 and the linear scales 181 and 182 as stated above, the movement of the lower chuck movers 162 and 165 can be controlled appropriately, so that the lower chuck 141 can be moved to a preset horizontal position.

Further, in the process S10, the lower chuck 141 is moved in the horizontal direction as stated above, and the position of the lower chuck 141 in the rotational direction (the direction of the lower chuck 141) is also adjusted by rotating the lower chuck 141 by the first lower chuck mover 162.

Thereafter, by moving the lower chuck 141 vertically upwards by the first lower chuck mover 162, position adjustment between the upper chuck 140 and the lower chuck 141 in the vertical direction is performed, so that position adjustment between the upper wafer W_(U) held by the upper chuck 140 and the lower wafer W_(L) held by the lower chuck 141 in the vertical direction is carried out (process S11 of FIG. 9).

In the process S11, when moving the lower chuck 141 vertically upwards by the first lower chuck mover 162, the lower chuck 141 is also moved in the horizontal direction as the base of the first lower chuck mover 162 has the wedge shape. Resultantly, the horizontal position of the lower chuck 141 adjusted in the process S10 is deviated.

Accordingly, as in the process S10, the position of the lower chuck 141 in the X direction is measured by using the first laser interferometer 176, and the position of the lower chuck 141 in the Y direction is measured by using the second laser interferometer 177. Further, the position of the first lower chuck mover 162 in the X direction is measured by using the first linear scale 181, and the position of the second lower chuck mover 165 in the Y direction is measured by using the second linear scale 182. Then, by servo-controlling the lower chuck movers 162 and 165 with the position loop using the measurement results of the laser interferometer system 170 and the speed loop using the measurement results of the linear scales 181 and 182, the position of the lower chuck 141 in the horizontal direction is corrected. Accordingly, the positions of the upper wafer W_(U) and the lower wafer W_(L) in the horizontal direction are corrected (process S12 of FIG. 9), and, thus, the upper wafer W_(U) and the lower wafer W_(L) are disposed to face each other at the preset positions.

Subsequently, a bonding processing of bonding the upper wafer W_(U) held by the upper chuck 140 and the lower wafer W_(L) held by the lower chuck 141 is performed.

First, as depicted in FIG. 10, the actuator 211 is lowered by the cylinder 212 of the pressing member 210. As the actuator 211 is moved down, the center of the upper wafer W_(U) is lowered while being pressed. At this time, the preset pressing load is applied to the actuator 211 by the air supplied from the electro-pneumatic regulator. The center of the upper wafer W_(U) and the center of the lower wafer W_(L) are pressed to be in contact with each other by the pressing member 210 (process S13 of FIG. 9). At this time, by stopping the operation of the vacuum pump 197 a, the vacuum-exhaust of the upper wafer W_(U) from the first suction openings 195 a in the first suction region 194 a is stopped, while carrying on the operation of the second vacuum pump 197 b to vacuum-exhaust the second suction region 194 b from the second suction openings 195 b. When pressing the center of the upper wafer W_(U) with the pressing member 210, the periphery of the upper wafer W_(U) can still be held by the upper chuck 140.

Accordingly, the bonding is started between the center of the upper wafer W_(U) and the center of the lower wafer W_(L) which are pressed against each other (as indicted by a bold line in FIG. 10). That is, since the front surface W_(U1) of the upper wafer W_(U) and the front surface W_(L1) of the lower wafer W_(L) have been modified in the processes S1 and S6, respectively, a Van der Waals force (intermolecular force) is generated between the front surfaces W_(U1) and W_(L1), so that the front surfaces W_(U1) and W_(L1) are bonded. Further, since the front surface W_(U1) of the upper wafer W_(U) and the front surface W_(L1) of the lower wafer W_(L) have been hydrophilized in the processes S2 and S7, respectively, hydrophilic groups between the front surfaces W_(U1) and W_(L1) are hydrogen-bonded (intermolecular force), so that the front surfaces W_(U1) and W_(L1) are firmly bonded.

Then, by stopping the operation of the second vacuum pump 197 b while still pressing the center of the upper wafer W_(U) and the center of the lower wafer W_(L) with the pressing member 210, the vacuum-exhaust of the upper wafer W_(U) from the second suction openings 195 b in the second suction region 194 b is stopped. Accordingly, the upper wafer W_(U) falls down on the lower wafer W_(L). The upper wafer W_(U) gradually falls on the lower wafer W_(L) to be in contact with each other, and the aforementioned bonding between the front surfaces W_(U1) and W_(L1) by the Van der Waals force and the hydrogen-bond is gradually expanded. Accordingly, the entire front surface W_(U1) of the upper wafer W_(U) and the entire front surface W_(L1) of the lower wafer W_(L) are brought into contact with each other, so that the upper wafer W_(U) and the lower wafer W_(L) are bonded (process S14 of FIG. 9).

In this process S14, since the rear surface W_(U2) of the upper wafer W_(U) is supported by the pins 191, the upper wafer W_(U) is easily separated from the upper chuck 140 when the vacuum-exhaust of the upper wafer W_(U) by the upper chuck 140 is released. Thus, the expansion (bonding wave) of the bonding between the upper wafer W_(U) and the lower wafer W_(L) takes place in a circular shape, so that the upper wafer W_(U) and the lower wafer W_(L) are appropriately bonded.

Thereafter, the actuator 211 of the pressing member 210 is raised up to the upper chuck 140. Further, by stopping the operation of the vacuum pumps 227 a and 227 b and thus stopping the vacuum-exhaust of the lower wafer W_(L) in the suction region 224, the attracting and holding of the lower wafer W_(L) by the lower chuck 141 is stopped. At this time, since the rear surface W_(L2) of the lower wafer W_(L) is supported by the pins 221, the lower wafer W_(L) is easily separated from the lower chuck 141 when the vacuum-exhaust of the lower wafer W_(L) by the lower chuck 141 is released.

Thereafter, the combined wafer W_(T) obtained by the bonding of the upper wafer W_(U) and the lower wafer W_(L) is transferred to the transition device 51 by the wafer transfer device 61, and then is transferred into the cassette C_(T) of the preset cassette placing table 11 by the wafer transfer device 22 of the carry-in/out station 2. Through these processes, the series of operations of the bonding processing for the wafers W_(U) and W_(L) is completed.

According to the exemplary embodiment as described above, by performing the hybrid control (servo control) using the laser interferometer system 170 and the linear scales 181 and 182 in the process S10, the positions of the lower chuck movers 162 and 165 in the horizontal direction can be appropriately adjusted. Further, even if the lower chuck 141 is deviated in the horizontal direction when it is moved in the vertical direction in the process S11, this deviation amount in the horizontal position can be measured by using the laser interferometer system 170 in the process S12. Then, by performing the hybrid control using the laser interferometer system 170 and the linear scales 181 and 182, the positions of the lower chuck movers 162 and 165 in the horizontal direction can be appropriately corrected. Accordingly, since the relative position between the upper chuck 140 and the lower chuck 141 can be appropriately adjusted, the bonding between the upper wafer W_(U) held by the upper chuck 140 and the lower wafer W_(L) held by the lower chuck 141 can be appropriately carried out later.

Moreover, since the bonding system 1 of the present exemplary embodiment is equipped with the surface modifying apparatus 30, the surface hydrophilizing apparatus 40 and the bonding apparatus 41, the bonding of the wafers W_(U) and W_(L) can be performed efficiently within the single system. Therefore, the throughput of the wafer bonding processing can be improved.

4. Other Exemplary Embodiments

Now, other exemplary embodiments of the present disclosure will be explained.

In the above-described exemplary embodiment, though the servo loop shown in FIG. 7 is used in the servo-control over the first lower chuck mover 162 and the second lower chuck mover 165, the exemplary embodiment is not limited thereto. For example, the servo loop may have a position loop and a speed loop using the measurement results of the linear scales 181 and 182, as shown in FIG. 11.

In such a case, the position of the first lower chuck mover 162 in the X direction is measured by using the first linear scale 181, and the position of the second lower chuck mover 165 in the Y direction is measured by using the second linear scale 182. Then, the lower chuck movers 162 and 165 are servo-controlled by using the position loop and the speed loop using the measurement results of the linear scales 181 and 182.

Thereafter, the position of the lower chuck 141 in the X direction is measured by using the first laser interferometer 176, and the position of the lower chuck 141 in the Y direction is measured by using the second laser interferometer 177. Further, a correction amount for the position of the first lower chuck mover 162 in the X direction and a correction amount for the position of the second lower chuck mover 165 in the Y direction are calculated from the measurement results of the laser interferometer system 170. Then, the lower chuck movers 162 and 165 are servo-controlled based on these correction amounts.

In the present exemplary embodiment, the same effects as obtained in the above-described exemplary embodiment can be achieved. That is, the relative position between the upper chuck 140 and the lower chuck 141 can be appropriately adjusted, and the bonding between the upper wafer W_(U) held by the upper chuck 140 and the lower wafer W_(L) held by the lower chuck 141 can be appropriately carried out later.

Further, in the present exemplary embodiment, the servo-control over the lower chuck movers 162 and 165 is performed by using only the measurement results of the linear scales 181 and 182, and by increasing a gain, the responsiveness can be bettered.

In the present exemplary embodiment, after the lower chuck movers 162 and 165 are servo-controlled by using the measurement results of the linear scales 181 and 182, the lower chuck movers 162 and 165 are further servo-controlled by using the measurement results of the laser interferometer system 170. In the above-described exemplary embodiment, however, the lower chuck movers 162 and 165 are hybrid-controlled by using the measurement results of the laser interferometer system 170 and the measurement results of the linear scales 181 and 182. As a result, the throughput of the wafer bonding processing can be improved.

Moreover, though the lower chuck 141 is configured to be movable in the horizontal direction in the bonding apparatus 41 according to the above-described exemplary embodiment, the upper chuck 140 may be configured to be movable in the horizontal direction instead. In such a case, the laser interferometer system 170 and the linear scales 181 and 182 may be provided at the upper chuck 140. Alternatively, both the upper chuck 140 and the lower chuck 141 may be configured to be horizontally movable. In such a configuration, the laser interferometer system 170 and the linear scales 181 and 182 may be provided at one of the upper chuck 140 or the lower chuck 141.

Further, though the lower chuck 141 is configured to be movable in the vertical direction in the bonding apparatus 41 according to the above-described exemplary embodiment, the upper chuck 140 may be configured to be vertically movable instead, or both the upper chuck 140 and the lower chuck 141 may be configured to be vertically movable.

In addition, though the lower chuck 141 is configured to be rotatable in the bonding apparatus 41 according to the above-described exemplary embodiment, the upper chuck 140 may be configured to be rotatable instead, or both the upper chuck 140 and the lower chuck 141 may be configured to be rotatable.

In addition, in the bonding system 1 according to the above-stated exemplary embodiment, after the wafers W_(U) and the W_(L) are bonded in the bonding apparatus 41, the obtained combined wafer W_(T) may be heated to a preset temperature (annealing processing). By performing this heating processing on the combined wafer W_(T), bonding interfaces can be firmly bonded.

From the foregoing, it will be appreciated that the exemplary embodiment of the present disclosure has been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the embodiment disclosed herein is not intended to be limiting. The scope of the inventive concept is defined by the following claims and their equivalents rather than by the detailed description of the exemplary embodiment. It shall be understood that all modifications and embodiments conceived from the meaning and scope of the claims and their equivalents are included in the scope of the inventive concept. In the present disclosure, the substrate is not limited to the wafer. The present disclosure is also applicable to various other types of substrates such as a FPD (Flat Panel Display), a mask reticle for photomask, and so forth.

EXPLANATION OF CODES

-   1: Bonding system -   2: Carry-in/out station -   3: Processing station -   30: Surface modifying apparatus -   40: Surface hydrophilizing apparatus -   41: Bonding apparatus -   61: Wafer transfer device -   70: Controller -   140: Upper chuck -   141: Lower chuck -   162: First lower chuck mover -   165: Second lower chuck mover -   170: Laser interferometer system -   174: First reflection plate -   175: Second reflection plate -   176: First laser interferometer system -   177: Second laser interferometer system -   181: First linear scale -   182: Second linear scale -   W_(U): Upper wafer -   W_(L): Lower wafer -   W_(T): Combined wafer 

We claim:
 1. A bonding apparatus configured to bond substrates, comprising: a first holder configured to vacuum-exhaust a first substrate to attract and hold the first substrate on a bottom surface thereof; a second holder disposed under the first holder, and configured to vacuum-exhaust a second substrate to attract and hold the second substrate on a top surface thereof; a mover configured to move the first holder and the second holder relatively in a horizontal direction; a laser interferometer system configured to measure a position of the first holder or the second holder which is moved by the mover; a linear scale configured to measure a position of the mover; and a controller configured to control the mover based on a measurement result of the laser interferometer system and a measurement result of the liner scale, wherein the controller includes a position loop and a speed loop, and is configured to servo-control the mover, and the measurement result of the linear scale is used in the speed loop.
 2. The bonding apparatus of claim 1, wherein the measurement result of the laser interferometer system is used in the position loop.
 3. The bonding apparatus of claim 1, wherein the controller is configured to servo-control the mover based on the measurement result of the linear scale, and configured to servo-control, by calculating a correction amount for a position of the mover in the horizontal direction from the measurement result of the laser interferometer system, the mover based on the correction amount.
 4. The bonding apparatus of claim 1, wherein a reflection plate is provided at a position of the first holder or the second holder, which is moved by the mover, to face the laser interferometer system.
 5. The bonding apparatus of claim 4, wherein a length of the reflection plate in the horizontal direction is equal to or larger than a moving distance of the first holder or the second holder, which is moved by the mover in the horizontal direction, and a length of the reflection plate in a vertical direction is equal to or larger than a moving distance of the first holder or the second holder, which is moved in the vertical direction.
 6. A bonding system equipped with a bonding apparatus configured to bond substrates, wherein the bonding apparatus comprises: a first holder configured to vacuum-exhaust a first substrate to attract and hold the first substrate on a bottom surface thereof; a second holder disposed under the first holder, and configured to vacuum-exhaust a second substrate to attract and hold the second substrate on a top surface thereof; a mover configured to move the first holder and the second holder relatively in a horizontal direction; a laser interferometer system configured to measure a position of the first holder or the second holder which is moved by the mover; a linear scale configured to measure a position of the mover; and a controller configured to control the mover based on a measurement result of the laser interferometer system and a measurement result of the liner scale, wherein the controller includes a position loop and a speed loop, and is configured to servo-control the mover, and the measurement result of the linear scale is used in the speed loop, wherein the bonding system comprises: a processing station equipped with the bonding apparatus; and a carry-in/out station configured to place thereon multiple first substrates, multiple second substrates or multiple combined substrates each obtained by bonding the first substrate and the second substrate, and configured to carry the first substrates, the second substrates or the combined substrates into/from the processing station, wherein the processing station comprises: a surface modifying apparatus configured to modify surfaces of the first substrate or the second substrate to be bonded; a surface hydrophilizing apparatus configured to hydrophilize the surfaces of the first substrate or the second substrate modified by the surface modifying apparatus; and a transfer device configured to transfer the first substrates, the second substrates or the combined substrates with respect to the surface modifying apparatus, the surface hydrophilizing apparatus and the bonding apparatus, and wherein, in the bonding apparatus, the first substrate and the second substrate having the surfaces hydrophilized by the surface hydrophilizing apparatus are bonded.
 7. A bonding method of bonding substrates by using a bonding apparatus, wherein the bonding apparatus comprises: a first holder configured to vacuum-exhaust a first substrate to attract and hold the first substrate on a bottom surface thereof; a second holder disposed under the first holder, and configured to vacuum-exhaust a second substrate to attract and hold the second substrate on a top surface thereof; a mover configured to move the first holder and the second holder relatively in a horizontal direction; a laser interferometer system configured to measure a position of the first holder or the second holder which is moved by the mover; and a linear scale configured to measure a position of the mover, and a controller configured to control the mover based on a measurement result of the laser interferometer system and a measurement result of the liner scale, wherein the controller includes a position loop and a speed loop, and is configured to servo-control the mover, wherein the bonding method comprises controlling the mover using a measurement result of the laser interferometer system and a measurement result of the linear scale to adjust a relative position between the first holder and the second holder, measuring the position of the first holder or the second holder by using the laser interferometer system; measuring the position of the mover by using the linear scale; and servo-controlling the mover by using the measurement result of the linear scale in the speed loop.
 8. The bonding method of claim 7, further comprising: servo-controlling the mover by using the measurement result of the laser interferometer system in the position loop.
 9. The bonding method of claim 7, further comprising: measuring the position of the mover by using the linear scale; servo-controlling the mover by using the measurement result of the linear scale; measuring the position of the first holder or the second holder by using the laser interferometer system; and calculating, from the measurement result of the laser interferometer system, a correction amount for a position of the mover in the horizontal direction, and servo-controlling the mover based on the correction amount. 